I have an older Airport Addicted, which is similar, but without the wheels.
The trick to efficient space utilization is to figure out how best to use the deeper (8") portion of the bag. If you have a 400/2.8 the lens hood is really large diameter and this will take some priority for this deeper space. I use the 8" deep space for my 70-200/2.8 IS which is stored vertically, lens cap straight downwards with the bag open and hood reversed. The lens is 8" long so this works out well.
I also store my 5DII with L bracket and handstrap with the left side of the camera down (handstrap up). 24-70/2.8 lens attached with hood attached (not reversed). This facilitates the quickest access to shooting; grab the handstrap side of the camera while in the bag, lift straight out, lens cap off and start shooting. My flash is also 8" long so it goes here.
Think Tank used to have more user pics of packing arrangements, but the revised web site has done away with most of these.
Mike K

When you said you store your 70-200 standing up in the deep end I could not figure out why I did not do that. So I went and stood it up and it was not even close. So I came back and re-read your post. I noticed you said IS and so I figured Canon. I had to go find the sizes of the the two. N 4x8.5" and C 4x8.06" and that is just about what I am off. It would zip but I would not want it banging into anything. So for me the only way is sideways.

Wickedfn4u wrote:
N 4x8.5" and C 4x8.06" and that is just about what I am off. It would zip but I would not want it banging into anything. So for me the only way is sideways.

Too bad, the Canon 70-200, 100-400 and Sigma 70-200 OS are all less than 8" long.
I also put a 135/2 lens in vertically and leave the hood mounted (8" long). Sometimes I carry extension tubes in the cavity made by the 135 hood.

I have a friend who used to carry a LF system in this bag and would use the 8" deep section of the bag to create 2 layers of equipment, with padding separating the two.